FileGizmo — Data & CSV tools
Flatten nested JSON
Flatten nested JSON objects into dotted or bracketed keys entirely in your browser.
Working locally…
Preparing the browser worker.
Complete
Your file is ready
Simple by design
Flatten nested JSON in three steps
FileGizmo flattens nested JSON objects into predictable key-value records without uploading configuration, API responses, or exports. Choose dotted notation such as customer.address.city or bracketed notation such as customer[address][city]. Arrays can remain compact JSON text or expand into indexed keys when each position needs its own field.
A top-level array is processed record by record, while a single object produces one flattened object. Empty objects and arrays are retained instead of disappearing silently. Key collisions are detected and reported rather than overwriting an existing value. Primitive top-level JSON values are rejected because they have no nested record structure to flatten.
The transformation runs in a dedicated browser worker and returns formatted UTF-8 JSON through the standard result contract. Flattening is useful before CSV conversion, spreadsheet export, form mapping, and analytics ingestion. Review arrays before expanding them: long or inconsistent arrays can create many sparse keys and may be better preserved as compact JSON. Dotted notation is concise, while bracketed notation can be clearer when original keys already contain periods.
- 1
Choose a JSON file
- 2
Select dotted or bracketed key notation and array handling
- 3
Flatten preview and download the JSON
Good to know
Frequently asked questions
How are nested keys named?
Choose dotted keys such as address.city or bracketed keys such as address[city].
How are arrays handled?
Keep arrays as compact JSON text or expand their indexes into separate flat keys.
Can it flatten an array of records?
Yes. Every object in a top-level array is flattened independently.
Does nested data leave the browser?
No. JSON parsing and flattening run locally in a dedicated worker.